It is recognized that the most dangerous of conditions at an airport is where there is danger of high speed collision involving an aircraft landing or taking off. This condition is called a runway incursion (RI) which, by definition is "any occurrence at an airport involving an aircraft, vehicle, or person on the ground that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to take off, landing, or intending to land." The frequency of these RIs has been increasing in recent years, along with the increased traffic load at airports. Although the incidences are still relatively rare, they are still very dangerous and collisions have occured with disastrous results in terms of injuries, loss of life and property.
There is a continuous effort by the Federal Aviation Administration (FAA), as well as by individuals and private companies, to improve airport safety and enhance the performance of air traffic controllers at United States airports. The primary safety mission of air traffic controllers is to prevent runway incursions. Runway incursions occur when aircraft or other vehicles enter a runway on which an aircraft has been cleared for landing or take off. A primary goal of the FAA initiative is to be able to automatically detect the occurrence of a runway incursion, and alert the responsible air traffic controller. Ideally, the safety system would automatically predict when a runway incursion is imminent and generate an alert prior to the intrusion.
The primary radar for surveillance and monitoring the movement of airport ground or surface traffic, is a special purpose, high-resolution surface radar known as the Airport Surface Detection Equipment (ASDE-3) radar. The ASDE-3 radar employs frequency agility and circular polarization to achieve significant improvement in aircraft detection during adverse weather conditions. The 60 revolution per minute digitally scan converted radar provides a display to a range of 5.5 kilometers, with a range resolution of approximately 3.7 meters and an azimuth beamwidth of 0.25 degrees.
Because of the ratio of target size to radar range, a jetliner can return energy in a very large number of range and bearing sample bins. Moreover, because of differences in reflectivity, the target may actually appear in the data as two or more smaller returns rather than one large one. In some cases, the radar image may look very much like the plan view of the aircraft itself, while, in others it may not.
The current method of tracking in the Airport Movement Area Safety System (AMASS) program involves detecting a region of greater radar return in the (.rho.,.phi.) of the radar signal and then computing a centroid from all the reflected energy of the target. That centroid location is then tracked using an Alpha-Beta tracker. Because different components of the aircraft can reflect energy differently, depending on aspect, the radar can miss portions of the aircraft on any one sweep. This can cause the centroid to exhibit significant jumps, which tends to confuse the tracker, especially during aircraft turns. This phenomena might result in the erroneous generation of an alert if the tracker output were being used to predict runway incursions. Such false alarms tend to limit the usefulness of the system and degrade the confidence of the user. Targets such as trucks, buses, and smaller aircraft that have smaller radar cross-sections do not exhibit the kinds of tracking anomalies produced by large jets.
It is an object of the present invention to provide an improved radar tracking system that reduces the likelihood of runway intrusions.
Another object of the present invention is a process of detecting and tracking the components of an aircraft rather than its center.
Another object of the present invention is a radar tracking system combining images from several aircraft components rather than from the aircraft center alone.
A further object of the present invention is a stick-figure tracker employing radar data extraction to measure the range and bearing of various individual aircraft components and tracking each individual component separately.
An additional object of the present invention is a data extraction process that measures the range and bearing of each tracked aircraft component and predicts the precise locations of critical aircraft physical components to give instantaneous information of any change in aircraft bearing between radar sweeps.